The natural draft cooling tower is a type of direct-contact cooling tower that is open to the air. It uses the principle of the heat exchanger to allow hot water from the system to be cooled by coming in direct contact with fresh air.
Hot and moisturized air rises to the top of the tower, while cold water gets collected at its base. This cooling tower is desirable for power plants that are located near load centers. This method does not require any cooling fans resulting in cost savings.
The natural draft cooling tower working includes evaporating a small amount of water which removes the heat from the water, and then the cooled water is recycled through the unit.
When heated water and fresh air are mixed, the latent heat of vaporization is released and it causes the water to decrease its temperature.